Chemical removal of an acid-soluble metal part in a deep well



Feb. 17, 1948. C W ETAL 2,436,197

CHEMICAL REMOVAL OF AN ACID-SOLUBLE METAL PART IN A DEEP WELL Filed Aug. 6, 1945 i i I INVENTORS. Pau/H Caro we ATTORNE Y5 Patented Feb; 17, 1948 METAnraR'r m AiliEE-KWELL;

ware

eevi e iee e r 4 'i ie Na .35%:-

. 3 tf 'a de p W61 "It re p ti ularl ncer i a im r ed' met od dt' cbnipinng-wens, traversing a plurality of strata in which a ch emically soluble casing section "lecated' oppo's'i te V a "s'el e'cte.d stratum is rei l t e. i i' mn e imii h h a emically soluble "seetionis'" included in the casing stringopposite a productive zonethe soluble sec- "tionsin1 'ade-of'aluifninumgor an aluminum alloy, and it s remav d fle t d by on d e twini'a quantity or hydrochloric acid,

disadvantage bt jthi's method which limits'its usefulness is that the-action of the acid is quite slow, so; that an inordinate amount-of time is -c nsi me'di'n thepperation and complete removal 'is-somwhat uncertain.

"A p'artic'ularf cbject of the invention is to provide anf imp'r ed method of, and composition for, chemically dissolving an aluminum or alumifnum alloy'partj 'suchas a casing section, inth'e bore of awellwher'eby complete rapid removal is acl'iieved. Other objects andadvantages will e l i bf ds- According 'to the invention dissolution of parts becomeapparent as the des cription of the inven- 01', equipment nade 0f aluminum or aluminum alloy in the well'is achieved bysubjectin the metal part to the cjorro'ciing'action 'of 'a'hydrochloric eteidsolutiq toiwhich has been added an aliphatic alcohol, saunas methyl alcohol, ethyl alcohol, isopropyl alcohol, tertiary butyl alcohol, ethylene glycol, and' glycerine. To prevent or reduce; attack by the acid solution onadjacent ferrous metal parts, when such are present,.an lnhibitor of such action may be. included in the acid solution. L

Thei'nvention may be morereadily understood 'fi om -the following detailed'desc'ription and ac- "companying drawing of a mode of carrying'out the invention, suchmodeillustrating but'oheof various ways in whichthe principle of theinven- Eu os maybe used. Inthe saiddrawingthe single insure illustrates schematically inyertical section es to the chemical removal 'rernove'the soluble'section 3 according to the in- -"spent or partially .spent'fsolvent so 1ution .is,di'sbasis of the known ,stoichiometricalrelationship per cent of magnesium, and about 0.3 percent of; chromium, the'bal'ance being alumihuml If desired, 1 iinallo'yed a1i mihum 'inay' be used? The aluminum or aluminum "alloy section is placed in the 'oasin'g string so that the section' is opposite a productive'zone' 4, the annular spacebetween the Casing string and the Well hole being 5 filled with cement 5. 'Su'ch well-construction is conventionalandformsno part of the invention.

In preparing the well for treatment so as to vention, the portion ofthe well below the productive "zone 4 is: bridged'as 'with' a filler '6,-and--a packer 1 is set in the casing at the top of t'he zone Lthereby to isolate for treatment. the portion of the well containing the soluble section.

The packer is provided withtai central passage for admittingthe outer tube 81 extending from the top of the well to just below the packerj. 'An'inner tube 9 is strungfthroug'hthe outer 'tube and ex.- tends: from; the topiof the Well to near the bottom of the soluble section.

After arranging the apparatus as described, the chemical solvent of hydrochloric acid to which .has; been added a suitable "aliphatic alcohol may be introduced through tube 9' so'- as to fill the space H) in the cased. portion'ofth well between the top of the bridge 6 and the bottom of thetube 8. As thebhemical solvent becomes spent byj dissol'ving the metal of thesoluble section 301? the casing, fresh solvent may be introduced,]if necessary, thereby displacing the .spent solution from the well through tube 8. It-ispreferable to continuously circulate the chemicalsolventihto the space l0 through tube 9 while-the placed throughgtube 8. The amount of solvent to employ depends: upon the concentrationjo'f l-ICl therein and the weight of the alumin um s'ec tiori to be removed; 'andmay be compu'ted-onthe between H01 and aluminum to form aluminum chloride (A101 For example, approximately 1.7 gallons of 25 per cent hydrochlOricjacid 'solu-j- 45 'Various concentrations oil-1C1 may be used sueh tion is required'pe'r pound of aluminum section.

as- .10.. to. ..35..'.perj.1 ent,, concentrations betw n about 15 and 20 per cent being preferred.

A suitable amount of one of the aforementioned aliphatic alcohols to use in the hydrochloric acid solution to increase its rate of attack on the acid-soluble section is between about 0.25 and 2 per cent of the weight of the acid solution,

' about 0.5 per cent being generally preferred.

In order to reduce or prevent attack by the usual small quantities such as 0.4 to 1.0 per cent of the Wei ht of the acid solution.

As the aluminum section of the ,casing dis-1 solves, the solution becomes heated due to the liberation of heat of neutralization and hydrogen a. is evolved which is allowed to'escape through;

pipe 8. The generation of heat is an advantage, as it speeds the reaction.

After the aluminum section has been removed, 7 the packer l and tubing strings 8 and 9 are removed so as to permit drilling out theceme'nt sheath ll opposite the zone 4 and removal of the bridge 6, if desired.

As illustrative of the increased rate of action of hydrochloric acid or aluminum alloy tubing brought about by the addition of a corrosion ac- :celeratorof an aliphatic alcohol, tests were made in which pieces of the tubing were subjected to the dissolving action of hydrochloric acid solution to which various aluminum corrosion accelerators were added. In conducting these tests 300 cc. lots of acid were placed in a calorimeter together with a piece of an aluminum alloy containing 0.2 per cent copper, 1 per cent magnesium, 0.4 per cent .silicon, 0.2 per cent chromium, the balance being aluminum, and the rate of dissolving of the aluminum alloy determined by observing from time to time the temperature attained by the reacting materials, In these tests the higher the temperature attained by the materials in a given =numberof minutes after the reaction begins the faster the dissolving of the aluminum alloy curs. Tables I and II present data so obtained.

TABLE I Rate of reaction of 15% hydrochloric acid solu-,

tion on aluminum alloy accelerated by 0.5% of an aliphatic alcohol I I Temperature PF.) of Reacting .Materials After- Aliphatic Alcohol Min. Min. Min. Min. Min

None (Blank) 86 108 162 220 220 ethyL- 86 108 165 220 220 Ethyl-.- 86 109 166 218 220 Isopropyl 86 108 169 217 220 Tertiary butyl 86 109 185 219 218 Ethylene glycol 86 107 163 219 220 Glycerine. T 86 113 182 220 218 The data'in the tables show that by adding an hydrochloric acid solution its rate of attack on aluminum alloy is increased. This is evident from the fact that the temperature of the reacting materials attains a higher value in less time when an aliphatic alcohol is present in the acid solution.

Although various aliphatic alcohols may be used according to the invention, tertiary butyl alcohol, isopropyl alcohol, and glycerine have been found most useful in practice, and of these three tertiary butyl alcohol is to be generally preferred.

The term aluminum used herein and the appended claims .is used to mean all grades of aluminummetal, and the term aluminum alloy" means alloys of aluminum containing at least about 80 per cent of aluminum.

We claim:

1. A method of removing from a well a metal part formed of aluminum and its alloys which comprises subjecting the part to the dissolving action of an aqueous solution containing from about 15 to per cent hydrochloric acid and from 0.25 to 2.5 per cent of an aliphatic alcohol selected from the group consisting of tertiary butyl alcohol, isopropyl alcohol and glycerin.

2. The method according to claim 1 in which the aliphatic alcohol is tertiary butyl alcohol.

3. The method according to claim 1 in which Temperature F.) 0iReactthe aliphatic alcohol is isopropyl alcohol. Concentration of Aliphatic mg Mammals 4. The method according to claim 1 in which Alcohol 0 5 30 45 the aliphatic alcohol isglycerlne. Min Min Min. Min. Min. PAUL CARDWELL LOUIS H. EILERS. Nmwlank) 32 i3, i5; 133 133,55 REFERENCES CITED 86 108 141 180 212 3g The following references are of record in the s so 10% 144 178 me of e patent: 3: 115 5% #8 iii UNITED STATES PATENTS 1 13 107 135 50 Number Name I Date 22 gig 2,024,718 Chamberlain Dec. 17, 1935 86 103 124 137 154 2,124,530 Loomis'et al July 26, 1938 22 2,189,799 Irons Feb. 13, 1940 86 108 127 143 m4 2,252,973 Hall et al. Aug. 19, 1941 53 }}g g; fl? 3; 2,261,292 Salnikov Nov. 4, 1941 .5% Glycerine so 109 131 152 110 2,292,208 De Groote et al Aug. 4,1942 

